The impact of climate change in Guanzhong from the Western Zhou Dynasty to the Qing Dynasty on the evolution of tomb layout

Abstract

The Guanzhong region, a major political and cultural center in ancient China, is known for its imperial and noble tombs with symmetrical, central-axis layouts that reflect hierarchical order and feng shui principles. These tombs, often aligned with mountains and rivers, symbolize “harmony between heaven and humanity.” Climate shifts from the warm, humid Western Zhou to the colder, drier Little Ice Age post-Song and Yuan dynasties significantly impacted agriculture, environment, and societal dynamics in Guanzhong. Using regression models and interdisciplinary theories, this study explores how climate change influenced tomb layouts, providing insights for modern climate-adaptive underground space design.

Introduction

The Guanzhong region is located in the northwest of China, surrounded by mountains and relatively enclosed in terrain. It faces the danger of Xiaohan to the east, Longshan to the west, Qinling Mountains to the south, and the Yellow River to the north, forming a natural military barrier and strategic location. In history, Guanzhong has been a battleground for military strategists since ancient times. Due to its geographical advantage of being easy to defend but difficult to attack, it is known as the “Land of Abundance”¹. During the Qin and Han dynasties, Guanzhong was the core area of the empire. After Emperor Qin Shi Huang unified China, the capital was Xianyang. In the Han dynasty, Chang’an was established as the capital, laying the political center position of Guanzhong in Chinese history. Most of the historical periods in the Guanzhong region belonged to the temperate monsoon climate, with distinct four seasons, relatively mild climate, fertile soil, and superior agricultural production conditions, suitable for the development of agricultural civilization. Especially the Weihe Plain, known as the “Eight Hundred Miles Qin River”, was an important grain producing area in ancient China². Culturally, Guanzhong is one of the birthplaces of Chinese civilization, and the ancient capital Xi’an carries the cultural heritage of multiple dynasties. The Guanzhong region served as a major intersection of ancient Chinese culture, economy, and politics, forming a distinctive Guanzhong culture with a profound historical and cultural heritage.

At the same time, as the political and cultural center of ancient China, the evolution of tomb chamber spaces in the Guanzhong region reflects broader shifts in social, religious, and political structures. During the early Zhou and Qin dynasties, tombs exhibited a highly hierarchical system, characterized by large-scale noble burials that emphasized elaborate underground construction and substantial material wealth. The Mausoleum of the First Qin Emperor exemplifies this trend, featuring not only impressive above-ground structures but also complex subterranean spaces filled with rich funerary objects, underscoring the social status and power of the deceased³.

By the Han Dynasty, tomb design became more standardized. Imperial tombs, such as those of Emperor Wu and Emperor Jing of Han, integrated above-ground and underground elements in a structured manner, often containing numerous pottery figurines, chariots, horses, and daily utensils intended to mirror real-life environments and social order. Tombs were frequently constructed in accordance with natural topography, reflecting a growing emphasis on harmonizing human activities with the surrounding landscape. From the Wei, Jin, Southern and Northern Dynasties through the Sui and Tang periods, tomb architecture gradually simplified in form yet continued to emphasize strategic placement within the natural environment. Imperial tombs of the Sui and Tang, including the Qianling and Zhaoling Mausoleums, were often situated in geographically prominent locations, reinforcing their symbolic role as expressions of political authority and cultural values⁴. During the Song, Yuan, Ming, and Qing dynasties, tomb spaces increasingly emphasized Confucian ethical principles and patrilineal systems. Civilian tombs, in particular, adopted more simplified forms with fewer burial objects, illustrating a societal shift toward ethical restraint and frugality. Overall, the transformation of tomb chambers in Guanzhong—from the opulent and complex structures of early periods to more simplified and integrated forms in later eras—mirrors the historical evolution of power dynamics, religious influences, and social ideologies.

If we observe the Guanzhong region from the perspective of natural geography, the overall trend of geographical and climatic changes in the region from warm and humid to relatively dry and cold over thousands of years from the Western Zhou Dynasty to the Ming and Qing Dynasties. From the Western Zhou Dynasty to the Qin and Han Dynasties, the climate in the Guanzhong region was relatively warm and humid, and the water resources in the Wei River Basin were abundant, suitable for agricultural production, which created the reputation of Guanzhong as the “Land of Abundance” during this period and promoted the prosperity of the strong Zhou, Qin, and Han cultures. The bountiful agricultural harvest laid the foundation for the Guanzhong region to become a political and cultural center, forming a strong centralization and splendid culture. However, starting from the Wei, Jin, Southern and Northern Dynasties period, the climate gradually cooled down and precipitation decreased. Especially in the late Tang Dynasty, the Guanzhong region was gradually affected by the trend of aridification, and agricultural production pressure increased. Climate change has led to the deterioration of the ecological environment, and the wars and economic decline in the late Tang Dynasty were partially affected by this change. During the Song, Yuan, Ming, and Qing dynasties, the climate in Guanzhong was continuously dry, water resources were scarce, and agricultural production declined, leading to Guanzhong gradually losing its position as the national political and economic center⁵.

In recent years, the study of tomb spatial evolution in the Guanzhong region has increasingly embraced interdisciplinary approaches, moving beyond traditional archeological perspectives to integrate insights from climatology, ecology, and digital technologies. While earlier research on Qin and Han imperial tombs focused primarily on structural features and social hierarchies, recent scholarship has expanded to examine how environmental and climatic factors influenced burial practices and spatial organization⁶. For instance, studies now correlate climatic fluctuations during the Han Dynasty with shifts in tomb construction techniques and site selections, reflecting adaptive responses to environmental stressors such as increased precipitation or drought conditions. This alignment with paleoclimatological data offers a nuanced understanding of how temporal climate variability shaped not only the practical but also the symbolic aspects of tomb layouts. The integration of advanced technologies like GIS and 3D modeling has further enriched this interdisciplinary dialogue, enabling sophisticated analyses of spatial patterns across time⁷. Researchers have begun to use these tools to model the impact of ecological changes on tomb distribution and design, though their application in the Guanzhong region remains limited. Current interdisciplinary work, such as the coupling of pollen data with stratigraphic records, provides promising insights into vegetation changes and their ceremonial implications, revealing how shifts in local ecosystems influenced the choice of tomb materials and locations⁸.

However, despite these advances, significant gaps persist. The application of modern technologies, such as dynamic spatial simulation and digital restoration, has not been fully explored, leading to an incomplete analysis of the overall evolution of tomb layouts. Moreover, interdisciplinary research, particularly involving climate science and ecology, often lacks systematic spatial analysis, which is crucial for understanding the complex interactions between environmental changes and tomb spatial structures. While studies have identified correlations between climatic events and tomb construction, they frequently fall short in simulating long-term environmental impacts or incorporating high-resolution temporal data⁹.

Recent publications highlight the potential for further interdisciplinary collaboration. Research on global urban greening and its mitigation of heat island effects demonstrates how similar methodologies could be applied to archeological contexts, exploring how environmental changes influenced the spatial evolution of tombs¹⁰. Additionally, studies on production-living-ecological spaces emphasize the importance of combining spatial quantification with functional analysis, an approach that could be adapted to examine the interplay between tomb spaces and their surrounding landscapes. In conclusion, while the field has made strides in integrating climatological and ecological perspectives, there is a critical need for more dynamic, environment-focused modeling and the fuller adoption of digital tools. Future research should prioritize interdisciplinary frameworks that combine high-resolution environmental data with spatial analysis to unravel the complex relationships between climate variability, ecological conditions, and the evolution of tomb structures in the Guanzhong region¹¹.

As a famous border area between nomadic civilization and agricultural civilization in Chinese history, the Guanzhong region has high ecological vulnerability¹². Climate change in the region will inevitably have a profound impact on its ecological environment, natural landscape, and ethnic cultural customs (Fig. 1). This study attempts to use ancient climate data and existing archeological materials, combined with theories from geography, sociology, architectural physics, environmental science, and anthropology, to clarify the impact mechanism of climate change on the layout and spatial form of tombs in the Guanzhong region from the Western Zhou Dynasty to the Ming and Qing Dynasties. It provides new research methods and data support for studying the evolution of tomb space in the Guanzhong region, and also provides important historical data and technical support for the climate adaptability of modern underground space design.

Fig. 1: 2023 Guanzhong regional GIS and population data.

a The location of the Guanzhong Plain. b GIS data of Guanzhong Plain.

Climate change significantly influences tomb architecture and location across different regions and cultures. This influence works through both direct environmental changes and indirect social adaptations. Shifts in temperature and precipitation affect where tombs are built, how they are designed, and how well they are preserved. These changes can lead to tombs being built in higher or lower areas, or in new geographic patterns. They also impact the choice of building materials and methods for preserving remains. For example, in China’s Jiangnan region—a low-lying area with many waterways and heavy rainfall—climate-related factors have strongly shaped burial practices. High groundwater levels and frequent flooding make deep burial difficult. As a result, people developed other interment styles, such as shallow graves, floating burials, and even above-ground tombs. At the same time, high population density and limited land have led to conflicts over burial space. This has encouraged more efficient practices, such as cremation and vertical burial. Similar patterns appear in other parts of the world. In Sweden, “liquid nitrogen burial” turns remains into plant-nourishing particles, and in Switzerland, ashes can be turned into diamonds. These innovations help adapt burial practices to cold climates and environmental values. In the United States, the green burial movement promotes biodegradable materials, reflecting growing ecological awareness. In ancient Egypt, long periods of drought likely contributed to the decline of the Old Kingdom, leading to simpler and smaller tombs as resources became scarce. These examples show that climate change is closely linked to variations in tomb forms and locations around the world. Regional social and environmental conditions play a key role in how these changes are expressed. In rainy areas, tombs often feature water-resistant and anti-corrosion designs. In dry areas, the focus is more on ground stability. Together, these responses demonstrate how deeply climate shapes human approaches to burial and cultural traditions.

Methods

Introduction to methods

In this study, a multiple regression model was employed to analyze the correlation between climate change and the spatial form and distribution characteristics of tombs in the Guanzhong region. This statistical approach allows for the simultaneous examination of multiple independent variables—such as temperature and precipitation—against dependent variables including geographical attributes (e.g., altitude, latitude, longitude) and structural features of underground tombs (e.g., tomb area, depth). The multiple regression model is particularly suited to this research due to its capacity to quantify the individual and collective effects of various climatic factors on archeological spatial patterns, thereby revealing underlying environmental adaptations and cultural responses.

Applicability of the method

The application of multiple regression in climate-archaeology interdisciplinary studies is highly appropriate, as it accommodates both continuous and categorical variables and can handle complex, multi-factorial systems where multiple influences interact. For instance, climate variables often exhibit collinearity, and the regression framework allows for diagnostics such as Variance Inflation Factor (VIF) to detect and mitigate multicollinearity issues. In this analysis, we incorporated climate proxy data, such as annual mean temperature and precipitation levels reconstructed from paleoclimatic records, alongside geospatial tomb data. To ensure robust results, we selected predictors based on theoretical relevance and preliminary correlation analyses. The model was specified with tomb spatial features, elevation, and geographic coordinates as dependent variables, and climate variables as independent variable.

Model parameter settings

Key parameters were carefully chosen to enhance model validity and interpretive power. The significance level (α) was set at 0.05, and p-values were used to evaluate the statistical significance of each predictor. The coefficient of determination (R²) and adjusted R² were applied to measure the model’s explanatory power, accounting for the number of predictors. Residual plots and normality tests (e.g., Shapiro-Wilk) were examined to verify that error terms met the assumptions of homoscedasticity and normal distribution. Furthermore, we conducted cross-validation to assess predictive accuracy and avoid overfitting.

The adaptability of the multiple regression model in this context lies in its ability to integrate quantitative climatic data with archeological observations, thereby bridging environmental science and historic interpretation. For example, the model can elucidate whether prolonged drought conditions correlated with deeper tomb constructions, possibly reflecting adaptive behavior to changing groundwater levels or temperature fluctuations. This approach not only reinforces the empirical rigor of archeological hypotheses but also aligns with contemporary interdisciplinary methodologies that seek to contextualize human cultural development within environmental narratives. Thus, the use of multiple regression adds methodological depth and analytical credibility to the exploration of climate-tomb interactions in the Guanzhong region.

Special note

In this study, while temperature and precipitation are used as core climate variables to investigate the impact of climate change on tomb design, the analytical framework has adequately accounted for potential confounding factors such as social status, warfare, cultural shifts, and technological advancements. The ability to indirectly control for these social factors through climate variables is based on the following reasons: First, large-scale, long-term climate change serves as a fundamental background force driving social stratification, uneven resource distribution, and differential adaptive strategies among groups. For example, during cold and dry periods, reduced agricultural output may exacerbate social inequality, leading elite groups to emphasize tomb scale and preservation techniques as a means to legitimize their power. Such behavioral differences are essentially social responses to climatic pressures; thus, temperature and precipitation variables inherently capture information related to resource allocation and behavioral patterns associated with status hierarchy. Second, historical large-scale wars, cultural transformations, and technological innovations are often closely linked to climate fluctuations. Prolonged droughts, for instance, can trigger conflicts over resources, while cold climates may stimulate adaptations in survival technologies or ritual changes. Although these factors are not explicitly included as variables in the model, they can be regarded as intermediate mechanisms or accompanying phenomena of climate influence. By controlling for long-term climate trends, the model effectively captures systematic signals of social, technological, and cultural changes triggered by climate. Finally, the multiple regression model employed in this study incorporates period-specific stratification and has statistically isolated the main effects of non-climatic factors, thereby allowing temperature and precipitation to more clearly extract the “net” climatic impact on tomb morphology. Therefore, although the model explicitly includes only temperature and precipitation as climate indicators, they embody deeper socio-environmental interactions, sufficiently controlling for confounding effects at a macroscopic level and ensuring the robustness of the conclusionsaryl.

Research scope and data sources

The study area of the Guanzhong region encompasses five cities and one district—Xi’an, Baoji, Xianyang, Weinan, Tongchuan, and Yangling—spanning ~55,623 square kilometers between 33°41'55″N to 35°39'40″N and 106°42'00″E to 110°35'40″E. Geographically, it comprises the alluvial plains of the Weihe River Basin and its tributaries, historically referred to as the “Eight Hundred Mile Qinchuan,” including the basins of the Wei, Jing, Feng, and Luo Rivers. Surrounded by mountains and traversed east–west by the Wei River, the region exhibits a distinctive basin climate and highly favorable conditions for agricultural development, rendering it a crucial cradle of ancient Chinese agricultural civilization (Fig. 1).

The tomb spatial data used in this study are derived primarily from publicly available sources provided by the Shaanxi Provincial Archeological Research Institute and the Xi’an Cultural Relics Protection Archeological Research Institute, among other official entities. Climate data are sourced from paleoclimatological publications by the Chinese Academy of Sciences and historical documentary records. It is important to note that only typical tombs were selected for analysis, as these are the only ones with systematically documented and publicly accessible archeological data. Many other burial sites have been either completely destroyed due to natural and anthropogenic factors or remain under protection status, which restricts archeological excavation and public data release. Therefore, the selection of tombs is both representative and necessitated by data availability¹³.

Results

Climate change and underground tomb layout and spatial form in the Guanzhong region during the Western Zhou, Spring and Autumn, and Warring States periods

From the Western Zhou to the Warring States periods, the Guanzhong region featured a warm and humid climate, with average annual temperatures around 15.5°C and precipitation ~700 mm, ideal for agriculture. Situated in the enclosed Wei River Basin with fertile soil and stable water supply, it became a cradle of early Chinese civilization and a long-term political-economic center. Although the climate turned drier by the late Warring States period, Guanzhong remained prosperous. Changes in temperature and precipitation are shown in Fig. 2¹⁴ (Fig. 2).

Fig. 2: Climatic Shifts in Guanzhong (Western Zhou–Spring & Autumn).

a Trend of Air temperature b Trend of Precipitation.

During the Western Zhou and Spring and Autumn periods, the layout of tombs in the Guanzhong region exhibited a strict hierarchical structure, reflecting significant social stratification between nobles and commoners¹⁰. Noble tombs, characterized by large vertical pit chambers, tomb passages, and accompanying burial pits, were meticulously arranged to emphasize ritual order and political power. Two representative examples, the Fengxiang Qin Gong Tomb and the Qin Dongling No. 1 Mausoleum, illustrate the spatial and structural sophistication of these burial practices¹⁵. The Fengxiang Qin Gong Tomb, located in Baoji City (107.36936°E, 34.472717°N), exemplifies early Qin royal tomb architecture. Situated on the Wei River Plain near the ancient capital Yongcheng, it features a “中”-shaped layout with dual sloped passages: the eastern passage extends 156.1 m, the western 85.5 m, and the entire structure spans 5334 m². The tomb chamber measures 59.4 m in length, 38.8 m in width, and reaches a depth of 24.5 m. Its interior includes a main coffin chamber (16 m × 8 m) and auxiliary rooms, demonstrating complex spatial organization aligned with hierarchical and ceremonial requirements. Qin Dongling No. 1 Mausoleum, near Xi’an (109.1943°E, 34.3675°N), adopts a “necropolis” layout with a central main tomb surrounded by subsidiary pits, chariot burials, and sacrificial sites. The mausoleum complex stretches 4000 m east-west and 1800 m north-south. Two parallel “Ya”-shaped tombs form the core, each with four sloping passages and side chambers. Each tomb measures ~57–58 m per side, with tomb passages up to 122.5 m long and a central chamber depth of around 24 m. The mound above reaches 250 m × 150 m, with a distinctive ridged surface¹⁶. These cases highlight how tomb spatial form—scale, depth, layout, and accompanying structures—served as material expressions of social status and ritual ideology in early Chinese civilization (Fig. 3).

Fig. 3: Guanzhong tomb spatial data (Western Zhou–Spring & Autumn).

a Tomb scene. b Tomb space. c Tomb location.

The impact of climate change during the Qin and Han dynasties on the layout and spatial form of underground tombs in the Guanzhong region

During the Qin and Han dynasties, the Guanzhong region exhibited a warm and humid climate, with an average annual temperature of ~14.5°C and annual precipitation around 650 mm, providing highly favorable conditions for agriculture. Located in the Wei River Basin and surrounded by mountains, the area benefited from concentrated spring and summer rainfall and abundant water resources from the Wei River and its tributaries, making it a key grain production base and the empire’s political-economic core¹⁷. Although a gradual drying trend emerged in the mid-to-late Han period, water conservancy projects and grain storage policies helped mitigate climatic impacts. Changes in temperature and precipitation are illustrated in the figure below (Fig. 4).

Fig. 4: Climatic shifts in Guanzhong (Qin–Han).

a Trend of air temperature. b Trend of precipitation.

The layout and spatial form of tombs in the Guanzhong region during the Qin and Han dynasties reflected strict social hierarchies and ritual culture, often situated according to feng shui principles—backed by mountains such as the Qinling or Beishan ranges and facing the Wei River—to emphasize both symbolic and defensive advantages. Tombs typically followed an axially symmetrical plan, featuring deep, straight passages, a central coffin chamber, and surrounding side chambers or pits for burial objects¹⁸. Peripheral structures such as chariot and horse pits further highlighted the status of the deceased. As case studies, the Han Ba Mausoleum and Han Yangling Mausoleum illustrate these characteristics. The Mausoleum of Emperor Wen of Han (Baling), located in Xi’an (109.0760°E, 34.2940°N), is a “Ya”-shaped vertical pit tomb with four passages on each side, totaling 135 m in length. The tomb chamber measures ~73 m per side and exceeds 30 m in depth, while the main coffin chamber is estimated to be 15–20 m long and 5–7 m wide. Its structure reflects Emperor Wen’s emphasis on frugality, with a modest number of burial objects such as pottery and bronze vessels¹⁹. The Han Yangling Mausoleum, the joint tomb of Emperor Jing and his empress near Xianyang (109.182639°E, 32.028181°N), exhibits a more complex “necropolis” layout with deep central passages and extensive peripheral pits containing figurines and daily items²⁰. The underground chamber is 71.5 m long, 74.5 m wide, and ~30 m deep, with a main coffin chamber measuring roughly 20–25 by 6–8 m. Its solemn, multi-chambered interior embodies the hierarchical and ceremonial grandeur of the mid-Western Han period. Together, these sites demonstrate how spatial organization, depth, scale, and surrounding structures materialized social order and imperial ritual in early imperial China(Fig. 5).

Fig. 5: Guanzhong tomb spatial data (Qin–Han).

a Tomb scene. b Tomb space. c Tomb location.

The impact of climate change during the Wei, Jin, Southern and Northern Dynasties on the layout and spatial form of underground tombs in the Guanzhong region

During the Wei, Jin, Southern and Northern Dynasties, the Guanzhong region experienced a distinct shift to a colder and drier climate, with average annual temperatures around 12.6°C and precipitation ~530 mm—significantly lower than previous periods²¹. This climatic deterioration contributed to reduced agricultural productivity, frequent droughts, and increased pressure on water resources, which in turn exacerbated socio-economic instability and political unrest. The changes in temperature and precipitation are illustrated in the figure below²² (Fig. 6).

Fig. 6: Climatic shifts in Guanzhong (Wei, Jin, Southern & Northern Dynasties).

a Trend of air temperature. b Trend of precipitation.

During the Wei, Jin, Southern and Northern Dynasties, tomb layouts in the Guanzhong region exhibited new characteristics shaped by Hu-Han cultural integration, featuring more diverse spatial structures. Vertical pit tombs with multi-chamber designs became prominent, often incorporating wide, deep passages and complex internal subdivisions. Brick-chamber tombs largely replaced earlier earthen structures among the elite, with lavish interior decorations such as murals and carvings reflecting social hierarchy and ritual practices. Burial objects—including pottery, gold and silverware, musical instruments, and horse gear—illustrated both aristocratic luxury and religious beliefs. Two representative examples are the Sixteen Kingdoms Tomb of Anding Liang and the Xiaoling Mausoleum of Emperor Wu of Northern Zhou²³. The Anding Liang Tomb in Xi’s Lintong District (109.2108°E, 34.4875°N) features a dual-chamber earth structure with a long sloping passage measuring 60.74 m in length and 11.86 m in depth. The tomb totals 80.74 m and includes a corridor, front chamber (3.4 m side length), and rear chamber (2.9 m side length, 2.4 m height), connected by an 0.8 m corridor. Artifacts recovered demonstrate a blend of northern ethnic and Central Plains cultures²⁴. Emperor Wu’s Mausoleum in Xianyang (108.7803°E, 34.4236°N) adopts a cross-shaped layout with a 31.5 m-long passage and five courtyards. The tomb extends 68.4 m, with a main chamber measuring 5.6 m in length and 4.3–4.5 m in width, reaching a depth of 10 m. Its symmetrical brick structure and partitioned ritual and burial spaces typify Northern Zhou imperial architecture¹⁶. These cases underscore how tomb design during this period reflected broader cultural hybridization and socio-ritual complexity²⁵ (Fig. 7).

Fig. 7: Guanzhong tomb spatial data (Wei, Jin, Southern & Northern Dynasties).

a Tomb scene. b Tomb space. c Tomb location.

The impact of climate change during the Sui and Tang dynasties on the layout and spatial form of underground tombs in the Guanzhong region

During the Sui and Tang dynasties, the Guanzhong region experienced a generally warm and humid climate, with an average annual temperature of ~15°C and precipitation around 700 mm, providing favorable conditions for agricultural development and supporting the area’s role as a key grain production base for the empire²⁶. This early climatic stability contributed significantly to economic prosperity and social cohesion in the early Tang. However, by the mid to late Tang, the climate became drier and cooler, leading to reduced rainfall, frequent droughts, and declining agricultural productivity. These changes exacerbated ecological stress and social unrest, forming an important backdrop to the political instability of the late Tang period²⁷. The variations in temperature and precipitation throughout the era are illustrated in the figure below (Fig. 8).

Fig. 8: Climatic shifts in Guanzhong (Sui–Tang).

a Trend of air temperature. b Trend of precipitation.

During the Sui and Tang dynasties, tombs in the Guanzhong region were strategically situated near mountains, rivers, or plains, reflecting feng shui principles aimed at ensuring eternal peace and prosperity for descendants. Concentrated in areas such as Mount Li and the Xianyang Plateau, these tombs often followed a symmetrical layout along a central axis, featuring sloping passages leading to multi-chamber structures comprising front and rear halls as well as side chambers. Built with brick or stone and occasionally decorated with murals or reliefs, the spatial organization emphasized solemnity and ritual propriety, reinforcing the period’s strict social hierarchy²⁸. The tomb of Sui crown prince Yang Yong in Tongguan County (110.244°E, 34.5428°N) exemplifies this tradition with its 63.8 m-long layout, including a 60 m passage and a circular main chamber (5.94 m wide, 5.72 m long) under a domed brick roof, reflecting both his status and Sui architectural restraint²⁹. Similarly, the Tang Jingling Mausoleum in Qian County (108.2543°E, 34.6078°N) extends 44.18 m with a central axis design, a 35.6 m stepped passage, and a brick-built chamber complex (5.8 m × 4.5 m) at 19.2 m depth, partitioned into ritual and burial zones with side chambers¹⁶. Together, these sites illustrate how spatial form, materials, and location expressed ritual norms and social identity in Sui-Tang tomb architecture (Fig. 9).

Fig. 9: Guanzhong tomb spatial data (Sui–Tang).

a Tomb scene. b Tomb space. c Tomb location.

The impact of climate change during the Song, Jin, and Western Xia dynasties on the layout and spatial form of underground tombs in the Guanzhong region

During the Song, Jin, and Western Xia dynasties, the Guanzhong region experienced a cold and dry climate, with average annual temperatures around 13.5°C and precipitation ~600 mm—significantly lower than in the Sui and Tang periods³⁰. Low temperatures, reduced rainfall, and frequent droughts adversely affected agricultural production, despite Song efforts to mitigate water shortages through irrigation projects. This climatic deterioration intensified during the Song-Jin wars, exacerbating ecological pressure and social instability. The cold, arid conditions also impeded socio-economic development in the Western Xia-controlled northwest. Overall, the persistent cold and dryness posed serious challenges to agriculture and regional stability. Changes in temperature and precipitation are illustrated in the figure below³¹(Fig. 10).

Fig. 10: Climatic shifts in Guanzhong (Song, Jin & Western Xia).

a Trend of air temperature. b Trend of precipitation.

During the Song, Jin, and Western Xia dynasties, tombs in the Guanzhong region were predominantly situated in the eastern hilly areas of the Guanzhong Plain, such as Lishan and Xianyangyuan, reflecting a deliberate emphasis on integrating with the natural environment. These tombs maintained the symmetrical layout tradition of the Sui and Tang periods, featuring sloping passages and multi-chamber structures—typically with a front chamber for rituals and a rear chamber for burial, often accompanied by side chambers for funerary objects. Constructed in brick with rigorous formality, the spatial organization emphasized solemnity and hierarchical order, illustrating the normative burial practices and socio-ritual concepts of the era³². The Northern Song tombs of the Meng and Lü families serve as representative examples. The Meng family tomb in Chang’an District, Xi’an (108.9069°E, 34.1590°N), exhibits a centrally symmetrical multi-chamber layout. Its trapezoidal passage measures 2.4–2.7 m in length and 0.7–1.35 m in width, leading to a brick burial chamber that is 2.75–3.15 m deep and 0.8–1.7 m wide, reaching about 5 m in depth³³. The Lü family cemetery in Lantian County (109.3175°E, 34.1568°N) spans 321 by 273 m and includes vertical shaft passages and earth-chamber tombs at depths of 7.5–15.5 m. The complex features varied structural types, such as single, double, and side chambers, with some tombs incorporating anti-robbery features like stacked empty chambers (Fig. 10). For instance, Lü Dalin’s tomb has a 2.7 m-long passage and a trapezoidal main chamber ~6 m long and 4 m wide, buried 15 mdeep with two decoy chambers above³⁴. Together, these sites demonstrate the continuity and adaptation of tomb design in response to cultural and environmental conditions during this period³⁵ Fig. 11.

Fig. 11: Guanzhong tomb spatial data (Song, Jin & Western Xia).

a Tomb scene. b Tomb space. c Tomb location.

The impact of climate change during the Yuan, Ming, and Qing dynasties on the layout and spatial form of underground tombs in the Guanzhong region

During the Yuan, Ming, and Qing dynasties, the Guanzhong region experienced a predominantly cold and dry climate, with an average annual temperature of ~12.3°C and precipitation around 530 mm. While the early Yuan period remained relatively warm and humid, conditions shifted toward colder and drier trends by the mid-Yuan, culminating in the pronounced “Little Ice Age” of the Ming–Qing transition³⁶. This period brought significantly lower temperatures, reduced rainfall, frequent droughts, and severe agricultural challenges, contributing to social instability. Although a slight warming occurred in the late Qing, the climate remained largely cold and arid, posing sustained constraints on regional production and development. Changes in temperature and precipitation are illustrated in the figure below³⁷(Fig. 12).

Fig. 12: Climatic shifts in Guanzhong (Yuan–Qing).

a Trend of air temperature. b Trend of precipitation.

During the Yuan, Ming, and Qing dynasties, tombs in the Guanzhong region were primarily distributed across the Guanzhong Plain and surrounding areas such as Xi’an and Xianyang, reflecting a continued emphasis on integrating with the natural environment. These tombs largely maintained an axially symmetrical layout with sloping or vertical passages and multi-chamber structures, often including front and rear halls as well as side chambers. Yuan tombs displayed a blend of Mongolian and Central Plains cultural features, favoring simpler and more practical designs, while Ming and Qing tombs emphasized stricter hierarchical and ritual norms, often using brick or stone construction for a more solemn and imposing appearance³⁸. The Liu Bolin family cemetery from the Yuan Dynasty, located in Chang’an District (108.9376°E, 34.1815°N), features a sloping passage ~10 m long leading to a brick-and-stone chamber measuring 6–8 m in length and 4–6 m in width and depth, with minimal decoration reflecting the period’s practical esthetic. In contrast, the Qing Dynasty Bayu aristocratic stone tomb complex in Dali County (109.49°E, 34.43°N) includes meticulously organized stone-built chambers with exquisite carvings. One representative tomb has an irregular convex-shaped chamber ~7–9 m long, 6 m wide, and 2.4 m deep, accessed by an 8 m-long passage (Fig. 13), illustrating the elaborate ritual practices and social status of Qing elite burials.

Fig. 13: Guanzhong tomb spatial data (Yuan–Qing).

a Tomb scene. b Tomb space. c Tomb location.

The correlation between the historical evolution of underground tomb layout and spatial form in Guanzhong region and climate change data

Based on previous research data, we have listed the Spatial form and climate data of underground tombs in the Guanzhong region from the Western Zhou, Spring and Autumn, Warring States, Yuan, Ming and Qing dynasties (Table 1), and then used the partial least squares regression (PLS) model in multiple linear regression to analyze the correlation between Spatial form and climate change³⁹ (Fig. 14).

Fig. 14: Climate change vs. tomb spatial form in Guanzhong.

a Guanzhong tomb area vs. climate. b Guanzhong tomb depth vs. climate. c Guanzhong tomb (passage/chamber length ratio) vs. climate.

Table 1 Historical climate and Spatial form data of underground tombs

Figure 14 illustrates the relationship between underground tomb structures in the Guanzhong region and climate change, particularly the influence of temperature and precipitation on tomb chamber area, depth, and the ratio of the tomb passage to the chamber’s long side. A variety of data visualization methods—including scatter plots, PLS regression coefficient plots, PLS component score plots, heatmaps, 3D scatter plots, and contour maps—are used to demonstrate how climate variables affect the structural features of tombs. The scatter plots reveal the relationships between temperature and tomb chamber area, depth, and passage-to-chamber ratio. In the analysis of chamber area, as temperature increases, the area initially expands and then stabilizes, indicating a nonlinear influence of temperature on chamber size. The scatter plot for tomb depth shows that rising temperatures lead to a gradual increase in depth, while precipitation has a relatively minor effect. The scatter plot for the passage-to-chamber ratio demonstrates an increasing trend with higher temperatures, suggesting that warmer conditions may facilitate the expansion of passage spaces. PLS regression coefficient plots and component score plots further clarify the impact of climate variables on tomb features. The regression coefficient plot indicates that temperature has a higher weighting influence on chamber area and depth, while precipitation plays a smaller role. The component score plot illustrates how tomb characteristics evolve under the combined effects of temperature and precipitation, reinforcing the conclusion that temperature is a more significant factor. The heatmap, using interpolated color gradients, displays patterns in chamber area, depth, and passage ratio under different climate conditions. It shows that both area and depth increase moderately under higher temperature and precipitation, with particularly noticeable changes in tomb dimensions in warmer regions. The passage ratio also rises with increasing temperature. 3D scatter plots and contour maps provide a more comprehensive perspective on the influence of climate factors. The 3D scatter plot reveals clear nonlinear trends among tomb area, depth, passage ratio, temperature, and precipitation, with rising temperatures generally corresponding to larger chambers and greater depths. The contour map visualizes predicted climatic impacts on tomb features, highlighting the complex relationships between temperature/precipitation variations and structural characteristics.

In summary, the data in Fig. 14 demonstrate that temperature significantly affects tomb chamber area, depth, and passage ratio. Higher temperatures generally lead to increased chamber dimensions and passage proportions, while precipitation has a comparatively minor influence on these structural features.

Based on previous research data, we have listed the geographical and climatic data of underground tombs in the Guanzhong region from the Western Zhou, Spring and Autumn Period, Warring States Period to the Yuan, Ming and Qing Dynasties (Table 2), and then used partial least squares regression (PLS) model to analyze the correlation between layout location and climate change (Fig. 15).

Fig. 15: Climate change vs. tomb geographical location in Guanzhong.

a Guanzhong tomb longitude vs. climate. b Guanzhong tomb latitude vs. climate. c Guanzhong tomb altitude vs. climate.

Table 2 Historical climate and geographical location data of underground tombs

Figure 15 illustrates the correlation between underground tombs in the Guanzhong region and climate change, specifically analyzing the influence of temperature and precipitation on the longitude, latitude, and elevation of the tombs. Through various visualization methods—including scatter plots, PLS regression coefficient plots, PLS component score plots, heatmaps, 3D scatter plots, and contour maps—the figure clearly demonstrates how these climatic factors affect the geographical features of the tombs and reveals trends in data variation under different climate conditions. The scatter plots show nonlinear relationships between temperature and the longitude, latitude, and elevation of the tombs. In the longitude analysis, tomb longitude exhibits fluctuating trends with temperature changes, though no clear unidirectional pattern is observed, indicating a complex influence of temperature on longitude. The latitude analysis suggests slight variations in tomb latitude with changes in temperature and precipitation, but these trends are not pronounced. Meanwhile, elevation shows a minor increasing trend with rising temperature, though the overall influence remains limited. The PLS regression coefficient plot indicates weak predictive effects of temperature and precipitation on longitude, latitude, and elevation, with regression coefficients close to zero, suggesting that climatic factors have minimal impact on these geographical features. The component score plot further illustrates the influence of temperature and precipitation as variables on tomb geography, with a dispersed score distribution reinforcing the limited role of climate factors in determining tomb locations. The heatmap, using interpolated color gradients, displays changes in tomb longitude, latitude, and elevation under different climate conditions. The results indicate that although climatic variations have some influence, the trends are relatively mild and lack significant linear relationships. The 3D scatter plot spatially represents the relationship between climate conditions and tomb features, confirming the weak influence of temperature and precipitation on tomb positioning. The contour map visualizes the predicted impact of climate change on tomb characteristics, with color gradients suggesting a potential—yet minimal—effect on geographical features.

Overall, the data analysis in Fig. 15 demonstrates that while climate change has some influence on the longitude, latitude, and elevation of the tombs, this influence is relatively small and does not exhibit clear or consistent patterns.

After completing the analysis of data computation results, this study attempts to analyze how climate change affects the layout and spatial form of underground tombs in the Guanzhong region from the perspectives of architecture, climatology, geography, geology, anthropology, and political economy.

Analysis of the reasons for the impact of climate change on the area and depth of tombs in the Guanzhong region

From the Western Zhou, Spring and Autumn Period, Warring States Period to the Yuan, Ming and Qing Dynasties, the area and depth of underground tombs in the Guanzhong region fluctuated but overall decreased, which is closely related to the impact of climate change on geological features and economic culture. During the Western Zhou Dynasty to the Spring and Autumn Period and Warring States Period, the climate in the Guanzhong region was warm and humid, and the soil structure was relatively stable, making it suitable for deep excavation and large-scale tomb construction. The warm and humid climate brings stable soil moisture, making the structure of the loess layer more compact and solid, and less prone to collapse. In this way, underground spaces are easier to excavate and maintain stability, which is beneficial for excavating larger tomb chamber chambers⁴⁰. At the same time, the moisture content of the soil improves the geological bearing capacity and can support large-scale underground structures. At the same time, warm and humid climate conditions have promoted agricultural harvests and socio-economic prosperity, resulting in larger tomb chamber scales and deeper tomb chamber chambers to showcase identity and social status. However, with the arrival of the late Eastern Han Dynasty and the Wei, Jin, Southern and Northern Dynasties, the climate gradually became cold and dry. Under the cold and dry climate conditions, the soil moisture of the loess in the Guanzhong Plain decreased, and the cohesion between soil particles decreased, resulting in loose and prone to collapse of the soil. When excavating tombs, it is difficult for the soil to form a stable structure, especially for large areas or deep tombs, which pose a greater risk of collapse and require more reinforcement materials and techniques, increasing the difficulty of construction. At the same time, the agricultural production reduction and social unrest brought about by climate change have affected the economy, resulting in a decrease in investment in tomb scale and a reduction in tomb area and depth. During the Sui and Tang dynasties, the climate briefly warmed up and the economy prospered, which once again led to a rebound in the scale of tombs, with the area and depth of tomb chamber chambers reaching new peaks. However, during the late Tang to Ming and Qing dynasties, the climate gradually became dry and cold, the soil became more loose, and the geological stability further declined. In addition, the increase in economic pressure further limited the scale of tombs, resulting in an overall decrease in the area and depth of tomb chamber chambers. The geological features and economic and cultural changes caused by climate change have led to a gradual decline in tomb chamber area and depth in fluctuations.

At the same time, during the warm and humid climate of the Western Zhou, Spring and Autumn, Warring States, Qin, Han, Sui, and Tang dynasties, the warm and humid soil environment of the Guanzhong Plain provided ideal conditions for the growth of microorganisms. Warm temperatures enhance the enzyme activity of microorganisms, accelerate their metabolic processes, and contribute to the decomposition of organic matter and nutrient cycling. And moist soil ensures water supply, making nutrients more easily absorbed by microorganisms. In addition, oxygen and nutrient mobility is better in humid environments, providing more suitable conditions for microbial reproduction and activity⁴¹. This warm and humid climate makes burial bodies and accompanying objects prone to decay in underground spaces. Therefore, tomb builders often bury the tomb chamber deep underground to prevent corrosion. As soil depth increases, oxygen supply decreases, and the deep soil environment tends towards hypoxia, which is not conducive to the growth of most aerobic microorganisms. At the same time, the temperature of deep soil is relatively stable, but it may also be low, resulting in poor moisture conditions and reduced microbial activity, which is more conducive to corrosion prevention. In the cold and dry climate of the Yuan, Ming, and Qing dynasties, the number and activity of microorganisms in the soil of the Guanzhong region were relatively low, and the bodies and burial objects in tombs were not easily decomposed⁴².

From the perspective of cultural ecology, the overall fluctuating decline in the area and depth of underground tombs in the Guanzhong region from the Western Zhou to the Yuan, Ming, and Qing dynasties can be attributed to the following mechanism: climate change influenced the regional economic foundation and social structure, which indirectly shaped the evolution of cultural ideologies, thereby determining the spatial form of tombs and funerary practices. During the Western Zhou, Spring and Autumn, and Warring States periods, the warm and humid climate in Guanzhong supported prosperous agriculture and pronounced social stratification. Ideologies such as the Confucian emphasis on ritual order and the Legalist focus on hierarchical norms became dominant, leading to large-scale noble tombs where deep burial and lavish funerary practices served as symbols of power and status. The Qin and Han dynasties, continuing under warm and humid conditions, saw the integration of Confucian filial piety with imperial centralization, further promoting the development of deep and expansive tombs, particularly evident in imperial mausoleums. From the Wei and Jin periods onward, a shift to colder and drier climates led to agricultural decline and social instability, fostering the rise of Daoist natural inaction and Buddhist concepts of reincarnation. Funerary concepts became simplified, and tomb scales noticeably contracted. During the Sui and Tang dynasties, a temporary return to warmer conditions led to a revival of Confucian ritual norms and a slight rebound in tomb scale, though it did not reach the levels of the Qin and Han periods, reflecting a tendency toward moderation. By the Song, Liao, Western Xia, Yuan, Ming, and Qing dynasties, the persistently cold and dry climate in Guanzhong, combined with resource constraints and multicultural integration, further catalyzed ideological transformation: Neo-Confucianism advocated for frugal burial ethics, and nomadic cultures incorporated practical funeral customs, resulting in generally reduced tomb depth and area, with greater emphasis on practicality and environmental adaptation. Throughout this long-term process, climate change—by impacting economic resources and social stability—indirectly guided the reconstruction of funerary concepts by Confucianism, Legalism, Daoism, and other ideological schools, ultimately manifesting as a gradual simplification and rationalization of tomb scale amid fluctuations⁴³.

From an architectural perspective, the overall decline in the scale and depth of underground tombs in the Guanzhong region from the Western Zhou through the Yuan, Ming, and Qing dynasties was closely tied to the evolution of aboveground architectural traditions influenced by climatic shifts. During the Western Zhou, Spring and Autumn, and Warring States periods, warm and humid conditions supported the construction of grand aboveground buildings with elevated rammed-earth platforms and sweeping roofs, reflecting ritual solemnity and authority. This was mirrored underground by tombs of considerable depth and spatial extent, designed to echo the symbolic power expressed in terrestrial architecture. The Qin and Han dynasties, which enjoyed similarly favorable climates, continued this tradition with large-scale, meticulously planned palaces and ritual compounds. Tombs from this era maintained significant depth and area, upholding the principle of constructing “residences for the afterlife” that corresponded to the grandeur of aboveground living spaces. As the climate turned colder and drier from the Wei, Jin, and Southern and Northern Dynasties onward, resource constraints led to simpler, more pragmatic aboveground structures. The spread of Buddhist and Daoist traditions further encouraged architectural modesty and spiritual introspection. These changes were directly reflected in tomb construction, which saw reduced dimensions and shallower depths. A temporary climatic warming during the Sui and Tang periods brought a revival of monumental aboveground architecture, though with greater emphasis on refined wooden structures and flexible spatial arrangements. This resulted in only a modest recovery in tomb scales. During the subsequent Song, Liao, Western Xia, Yuan, Ming, and Qing dynasties, persistently cold and arid conditions—coupled with Neo-Confucian values emphasizing frugality—drove aboveground architecture toward utilitarian simplicity. While brick and stone became more common, overall building scales contracted considerably. Tombs followed this trend, exhibiting markedly reduced depths and footprints while prioritizing durability and functional adaptation. Throughout this entire period, the spatial characteristics of underground tombs consistently reflected the prevailing aboveground architectural culture, which itself evolved in response to climate-mediated changes in material resources, construction technologies, and ideological values—ultimately manifesting as a pronounced trend toward simplification in both architectural domains⁴⁴.

Analysis of the reasons for the impact of climate change on the ratio of long sides of tomb passages and chambers in the Guanzhong region

During the Wei, Jin, Southern and Northern Dynasties and early Sui Dynasty, the climate in the Guanzhong region was relatively cold and dry, with low groundwater levels and low soil moisture. In dry and cold climate conditions, loess is relatively loose, and the geological bearing capacity is relatively weak. Horizontal excavation of large areas of space is more prone to collapse. The elongated underground space becomes a stable choice in this situation, as the elongated design reduces the lateral width while extending longitudinally, helping to disperse soil pressure, reduce the risk of collapse, and maintain the structural stability of the tomb chamber. However, during this period, the Guanzhong region remained the political and cultural center of China, a geographical space where power was concentrated. Therefore, the tombs in the Guanzhong region were still dominated by royal tombs, which often required a certain scale to reflect their feudal status and also required certain depth of protection for tomb anti-theft measures. However, there is a clear contradiction between poor soil conditions and the political demand for scale and depth. This contradiction is reflected in the spatial form of this elongated linear underground tomb. Through the narrow tomb passage, the depth and scale of the underground tomb chamber can be ensured, as well as the stability of the tomb and surrounding soil structure⁴⁵.

During the Western Zhou, Qin, and Han dynasties before the Wei, Jin, Southern and Northern Dynasties, the climate in the Guanzhong region was relatively warm and humid, with high soil moisture content and relatively tight and stable geology. The wetter loess layer can provide better bearing capacity, so there is no need to build excessively long tomb passages to support or protect the structure of the tomb chamber. A shorter tomb passage could meet the stability requirements of the royal tomb chambers at that time, avoiding additional excavation of soil. After the Sui and Tang dynasties, as well as the Yuan, Ming, and Qing dynasties, the political and cultural center of China shifted from the Guanzhong region to Jiangnan and North China. Since the Sui and Tang dynasties, there have been no large-scale tombs at the level of royal tombs in the Guanzhong region, and there is no need for scale and depth. Therefore, ultra long tomb passages and linear underground spaces have exited the historical stage⁴⁶.

From the perspective of cultural ecology, the evolution of tomb passage length relative to chamber proportions in the Guanzhong region reflects a dynamic interplay between climate shifts, ideological adaptations, and funerary practices across dynasties. During the Wei, Jin, Southern and Northern Dynasties through the Sui and Tang periods, tomb passages elongated significantly compared to the shorter passages of the preceding Western Zhou, Qin, and Han eras, while the subsequent Yuan, Ming, and Qing periods saw further shortening. This pattern emerged as climate change indirectly shaped cultural ideologies—such as Confucianism, Legalism, and Daoism—which in turn influenced spatial design in burial customs. In the Wei, Jin, and Southern and Northern Dynasties, a shift to colder, drier conditions triggered agricultural decline and social instability. Daoist principles of “natural non-action” and Buddhist concepts of reincarnation gained prominence, promoting simplified and adaptive burial practices. However, persistent political centralization and status symbolism required tombs to balance scale and structural stability amid resource constraints. Elongated passages reduced excavation risks in unstable, dry loess soils while maintaining ritual significance through linear spatial organization, embodying a cultural ethos that merged reclusion with order. During the Sui and Tang, a temporary climatic warming facilitated a partial revival of Confucian rituals, yet broader social inclusivity and the integration of Buddhist-Daoist beliefs into daily life encouraged elongated passages as a pragmatic compromise. This design accommodated both hierarchical traditions and geological conditions. In contrast, the warm, humid climates of the Western Zhou, Qin, and Han periods supported stable soils and overt power displays aligned with Confucian-Legalist ideologies, enabling shorter passages to suffice for large-scale chambers without structural reinforcements. By the Yuan, Ming, and Qing eras, prolonged cold-dry conditions, Neo-Confucian advocacy for frugal burials, and influences from nomadic practicality led to thorough simplified, functional tombs. Short tomb passage became cost-effective necessities, reflecting a cultural pivot toward secularization and utility⁴⁷.

From an architectural perspective, the significant elongation of the ratio between the tomb passage and the long side of the burial chamber in the Guanzhong region during the Wei, Jin, Southern and Northern Dynasties to the Sui and Tang periods—compared to the relatively shorter passages of the earlier Western Zhou, Qin, and Han eras and the even shorter ones of the Yuan, Ming, and Qing periods—is closely linked to the evolution of aboveground traditional architectural culture under the influence of climate change. During the Wei, Jin, and Southern and Northern Dynasties, colder and drier conditions led to resource constraints, causing aboveground structures to become simpler, lighter, and more utilitarian. The growing influence of Buddhism and Daoism further encouraged an introverted architectural style. Tombs needed to balance stability and symbolism amid limited resources, and elongated passages reduced the risk of lateral excavation collapse while maintaining ritual depth through linear spatial design. In the Sui and Tang periods, a temporary return to warmer climate revived monumental aboveground architecture, but the technological focus shifted toward flexible layouts and structural refinement. The elongation of tomb passages served as a compromise between ceremonial requirements and geological adaptability. In contrast, during the warm and humid Western Zhou, Qin, and Han periods, aboveground architecture emphasized grand scale and ritual solemnity, allowing shorter passages to suffice for large-scale chamber construction. By the Yuan, Ming, and Qing dynasties, persistently cold and dry conditions, coupled with Neo-Confucian advocacy for frugality, drove aboveground architecture toward simplicity and practicality. Tombs, influenced by these trends, adopted shorter passages as a cost-effective and efficient solution. Thus, changes in tomb passage proportions fundamentally reflect the evolution of aboveground architectural culture, which itself continuously adapted in response to climate-induced shifts in resources, technology, and ideology⁴⁸.

Analysis of the reasons for the impact of climate change on the latitude, longitude, and altitude of underground tombs in the Guanzhong region

During the Western Zhou, Spring and Autumn Period, Warring States Period, and Qin and Han Dynasties, the climate in the northern part of the Guanzhong region was relatively warm and humid, suitable for large-scale cultivation. The loess layer was relatively stable, so people tended to build tombs in the western and northern areas with higher terrain. The soil in these areas was relatively solid and could support deeper burial chambers. However, as time passed, the climate gradually turned dry and cold, especially after the Tang Dynasty, when the moisture in the loess layer gradually decreased, the soil became loose, and the geological stability decreased. Especially in areas with higher terrain and thicker loess layers, collapse was more likely to occur. To ensure the safety of tombs, the selection of burial sites is gradually shifting towards the southeastern region with lower terrain and denser soil.

At the same time, the dry and cold climate has led to the deterioration of agricultural production conditions, and the relatively warm and humid plain areas in the southeast have gradually become the center of agriculture. The selection of burial sites is beginning to move closer to these prosperous areas, not only because the concentration of population and economic activities has brought more funeral needs, but also because tombs are often located close to important life centers in terms of economy and culture. In addition, after the shift of economic center to the south, the development of Jiangnan and Central Plains regions has driven the prosperity of culture in the southeast direction, making tomb sites more inclined towards the southeast direction. For altitude, before the Song Dynasty, underground tombs in the Guanzhong region were mainly composed of royal tombs, and burial locations were often chosen at high places to show status and dignity. With the rise of the simple concept of common culture in the Song Dynasty, funeral culture gradually shifted from pursuing high standards to being restrained and practical, closer to sunrise life, and tomb locations were no longer limited to highlands far away from settlements. Therefore, the location of the tombs gradually decreased in altitude to adapt to economic and cultural changes. Of course, this is the main pattern of tomb distribution, and it cannot be ruled out that some residential tombs were still located in high-altitude mountainous areas after the Song Dynasty, as well as in the northwest region of Guanzhong⁴⁹.

From the perspective of cultural ecology, the overall trend of lowering elevation and eastward shift in the selection of underground tomb sites in the Guanzhong region from the Western Zhou to the Yuan, Ming, and Qing dynasties was primarily driven by climate change, which indirectly influenced economic foundations and social structures, thereby prompting adjustments in cultural ideologies. During the Western Zhou, Spring and Autumn, and Warring States periods, the warm and humid climate in Guanzhong supported advanced agriculture, while Confucian and Legalist ideologies emphasized ritual order and hierarchical symbolism. Noble tombs were predominantly located in high-altitude areas of the western Loess Plateau, leveraging elevated terrain to demonstrate authority and mitigate flood risks. The Qin and Han dynasties, continuing under warm and humid conditions, saw imperial mausoleums still favoring highland sites. However, with the development of the central Guanzhong Plain, tomb distribution began to shift eastward. From the Wei, Jin, and Southern and Northern Dynasties onward, colder and drier conditions led to agricultural decline and social instability, fostering the popularity of Daoist naturalistic concepts and Buddhist simplicity. Funerary practices increasingly prioritized practicality and resource adaptation, prompting a shift of tomb sites to lower-elevation southeastern areas with more stable soil conditions. This move aimed to reduce construction challenges and align with emerging agricultural economic centers. During the Sui and Tang periods, a temporary return to warmer climate saw a revival of Confucian rituals, yet the integration of Buddhist and Daoist ideas into secular life continued. Tombs further migrated eastward, often distributed in medium-altitude transitional zones between plains and hills, balancing ceremonial needs with geographical stability. From the Song, Liao, and Western Xia to the Yuan, Ming, and Qing dynasties, persistently cold and dry conditions, coupled with Neo-Confucian advocacy for frugal burials and the practical influences of nomadic cultures, drove tomb locations further east into low-altitude plain areas. This shift reflected a focus on functionality and cost efficiency, bringing tombs closer to population centers and economic hubs. Notably, some Qing Dynasty noble tombs remained in high-altitude areas, primarily due to the perpetuation of traditional burial customs in mountainous terrain by the ruling elite and the use of elevated sites to emphasize political authority and ethnic identity—a result of intertwined cultural traditions and political symbolism. Overall, the impact of climate change on tomb location was relatively limited, as it operated indirectly by constraining resources and economic activities rather than serving as a direct determinant⁵⁰.

From an architectural perspective, the gradual decrease in elevation and overall eastward shift in the selection of underground tomb sites in the Guanzhong region from the Western Zhou to the Yuan, Ming, and Qing dynasties were closely linked to the evolution of aboveground traditional architecture influenced by climate change. During the warm and humid Western Zhou, Spring and Autumn, and Warring States periods, aboveground structures often utilized elevated rammed-earth platforms to emphasize ritual authority, leading tombs to be correspondingly located in high-altitude western areas for flood and moisture avoidance. The Qin and Han dynasties, continuing under warm and humid conditions, featured large-scale aboveground palaces, with tombs maintaining high-altitude distributions while beginning to extend eastward. The colder and drier climate of the Wei, Jin, and Southern and Northern Dynasties caused aboveground architecture to become simpler and more practical due to resource constraints. The spread of Buddhism and Daoism promoted introverted architectural development, and tombs shifted to lower-altitude southeastern areas to reduce construction challenges. During the Sui and Tang periods, a temporary return to warmer conditions saw aboveground architecture regain grandeur but with greater emphasis on layout flexibility, leading tombs to continue moving eastward to transitional zones between plains and hills. From the Song, Liao, and Western Xia to the Yuan, Ming, and Qing dynasties, persistently cold and dry conditions, along with Neo-Confucian frugality and nomadic pragmatism, drove aboveground architecture toward simplification. Tombs fully shifted eastward to low-altitude plain areas closer to economic centers. The exceptional case of Qing Dynasty noble tombs selecting high-altitude sites was primarily due to the ruling class’s continuation of mountainous burial traditions and political symbolic needs, rather than climate adaptation considerations. Overall, the impact of climate change on tomb locations was relatively weak, as it primarily operated indirectly by influencing resource availability and cultural ideologies⁴.

Discussion

As shown in Table 1 and Fig. 14, from the Western Zhou Dynasty to the Ming and Qing Dynasties, the size of underground tombs in the Guanzhong region exhibited fluctuations against a background of overall declining temperature and precipitation, with tomb area displaying a general decreasing trend. Specifically, from the Western Zhou, Spring and Autumn, and Warring States periods to the Qin and Han Dynasties, tomb area increased markedly. In contrast, from the Qin and Han Dynasties to the Wei, Jin, Southern and Northern Dynasties, tomb area decreased noticeably. A modest increase in tomb area was observed from the Wei, Jin, Southern and Northern Dynasties to the Sui and Tang Dynasties, followed by a decline during the Song, Jin, and Western Xia periods. During the Yuan, Ming, and Qing Dynasties, tomb area then experienced a slight recovery. Regarding tomb depth, similar fluctuations occurred alongside the general cooling and drying trend from the Western Zhou to the Ming and Qing Dynasties, with an overall trend toward shallower tombs. From the Western Zhou through the Spring and Autumn, Warring States periods to the Qin and Han Dynasties, tomb depth increased moderately. A pronounced decrease in depth occurred from the Qin and Han Dynasties to the Wei, Jin, Southern and Northern Dynasties, followed by an increase from the Wei, Jin, Southern and Northern Dynasties to the Sui and Tang Dynasties. Thereafter, from the Sui and Tang Dynasties to the Yuan, Ming, and Qing Dynasties, tomb depth in the Guanzhong region continued to decrease⁵¹.

The ratio of tomb passage length to chamber length serves as an indicator of the overall spatial morphology of the underground tomb structure. When this ratio is large—typically resulting from a tomb passage longer than the long side of the chamber—the underground layout tends to exhibit a linear distribution. Conversely, a small ratio suggests a more planar spatial arrangement. In the Guanzhong region, during the Wei, Jin, Southern and Northern Dynasties, as well as the Sui and Tang Dynasty, the ratio of tomb passage length to chamber length exceeded 5, indicating a predominantly linear tomb space. In other periods, this ratio remained below 3, reflecting a generally planar tomb layout. According to the Partial Least Squares (PLS) component score analysis in Fig. 14, temperature appears to be the dominant factor influencing the spatial morphology of tombs, while the influence of precipitation is considerably weaker in comparison⁹.

As shown in Table 2 and Fig. 15, against a background of long-term cooling and drying, the distribution of tombs in the Guanzhong region generally shifted eastward and southward from the Western Zhou to the Ming and Qing dynasties. Although the average burial altitude gradually decreased over this period, a distinct exception is observed during the Qing Dynasty, when elite tombs—especially those of Han Chinese aristocratic families—were often constructed at elevations above 1000 m. This preference for higher elevations differentiated Qing aristocratic practices from those of the commoners and scholar-officials of the earlier Song and Ming dynasties, suggesting the involvement of cultural and strategic factors. Influenced by Feng Shui principles, which emphasized elevated terrain for better qi flow and spiritual safeguarding, these elites also took into account geographical advantages such as natural defensibility and lower erosion risk. Moreover, the choice of high-altitude burial sites fulfilled socio-cultural functions, serving as expressions of family status, enduring legacy, and territorial identity. Among climatic variables, temperature showed the strongest association with tomb location, though its overall influence was moderate; precipitation, by comparison, had a relatively limited effect. Analytical results indicate that climate variables exerted limited and non-linear influences on the geographical characteristics of tombs, with temperature variations showing weak and inconsistent correlations with longitude, latitude, and elevation. Overall, while climate—particularly temperature—had a detectable influence on the spatial distribution of tombs, its impact remained relatively subtle and exhibited no strong systematic pattern. The observed variations imply that non-climatic factors—such as cultural traditions, geomancy, social status, and political symbolism—likely contributed more substantially to tomb location decisions throughout this period⁵².

In this study investigating the impact of climate change on tomb spatial distribution and location in the Guanzhong region, although drought and flood severity indices were not directly employed, the selected temperature and precipitation indicators capture key climatic mechanisms associated with drought and flood phenomena. Fundamentally, droughts and floods arise from specific spatiotemporal patterns of precipitation and temperature: extended high temperatures intensify evaporation and contribute to drought conditions, while sustained heavy precipitation may lead to flooding. As essential climate variables, temperature and precipitation help regulate hydrothermal balance and influence regional moisture availability as well as the occurrence of droughts and floods. In Guanzhong—a region characterized by uneven seasonal precipitation distribution and considerable interannual variability—variations in precipitation and temperature can affect groundwater levels, soil erosion rates, and geological hazard probability. These environmental conditions may consequently influence tomb site selection, burial depth, and structural durability. By utilizing long-term, high-resolution temperature and precipitation data, this study represents physical climatic processes relevant to drought and flood formation, thereby indirectly addressing potential impacts of hydrological extremes on tombs. Furthermore, since drought and flood severity are typically derived from precipitation and temperature observations, these direct climate variables provide adequate explanatory capacity to analyze climate-tomb relationships within the scope of this research⁵³.

By examining the historical evolution of the layout and spatial configuration of underground tombs in China’s Guanzhong region, this study offers theoretical and technical insights applicable to the design and construction of contemporary underground spaces. Although ancient underground structures primarily served as burial sites—housing the deceased and funerary objects—their designers and builders were nevertheless concerned with preserving the contents from decay and mold. Consequently, tomb chambers were designed with consideration for the internal microclimate, aiming to establish a sealed, dry environment conducive to long-term preservation and to inhibit deterioration of objects. Attention was also given to waterproofing, drainage, and sealing techniques. In contrast, modern underground spaces—such as parking garages, subway stations, and shopping malls—serve more diverse and active functions. These spaces are not merely for storage but accommodate human occupancy and activity. As a result, they are not fully enclosed; instead, they require effective ventilation, high air quality, and thermal comfort to meet the needs of their users. Despite these functional differences, both historical tombs and modern underground structures share a common need: to maintain a suitable microclimate that ensures the preservation of contents—whether artifacts or goods—and safeguards against premature degradation⁵⁴.

Currently, modern underground spaces are commonly equipped with natural or mechanical ventilation systems and air quality monitoring systems. Nevertheless, during the design and construction phases, careful consideration should still be given to local climatic conditions, soil properties, and variations in groundwater levels, in order to mitigate the intrusion of detrimental elements—such as groundwater, bacteria, and fungi—that could compromise the microclimate and indoor environment of these spaces. Consequently, the traditional construction knowledge embodied in ancient underground tombs remains a valuable source of reference.

During the Western Zhou, Spring and Autumn, Warring States, Qin, Han, Sui, and Tang dynasties, the Guanzhong Plain was characterized by a humid climate. The groundwater table during these periods was generally shallow, typically lying between 1 and 10 m below the surface. Accordingly, underground tombs from these eras were usually constructed at depths greater than 10 m. In the warmer and more humid phases, such as the Western Zhou and Spring and Autumn periods, some tombs reached depths of up to 30 m. These tombs were often situated below the groundwater level, with larger-scale tombs generally buried deeper and located farther from saturated zones⁵⁵. This practice helped reduce the risk of groundwater infiltration into the tomb chambers, thereby slowing the decay of burial objects. In contrast, during the Wei, Jin, Southern and Northern Dynasties, the Song dynasties, and the Yuan, Ming, and Qing dynasties, the Guanzhong Plain experienced predominantly semi-arid to arid conditions. Groundwater levels during these periods were deeper, typically ranging from 10−30 m or more. Reduced precipitation and limited surface water infiltration contributed to the lower water table. Tombs from these dynasties were generally constructed at depths of less than 10 m and were often located above the groundwater zone, thus largely avoiding areas of water accumulation. During colder and drier periods, situating tombs away from groundwater-saturated areas not only minimized water intrusion but also helped mitigate potential damage to the tomb structure caused by seasonal freeze-thaw cycles in spring and winter. Additionally, the floors of tomb chambers were often sloped, and concealed drainage channels were incorporated around the chambers. These features likely contributed to reducing groundwater-related disturbances⁵⁶.

Therefore, the design of modern underground spaces may benefit from adopting certain principles observed in ancient tomb construction. In areas with a high groundwater table, functional underground spaces should be situated below the saturated zone. Conversely, in regions where the groundwater level is deep, such spaces may be positioned above the phreatic layer. Additionally, incorporating sloped floors and drainage channels within underground structures can help manage water accumulation. These measures can help mitigate groundwater intrusion, which may otherwise affect the microclimate and thermal conditions of underground functional areas. They may also reduce potential damage to the enclosing structure of the underground space caused by freeze-thaw cycles in the surrounding soil. Collectively, such strategies contribute to maintaining a more stable indoor environment and structural integrity in modern underground constructions.

Although underground tombs constructed during warm and humid periods in the Guanzhong region were designed with consideration of the contemporary climatic conditions and groundwater levels, the lack of scientific climate forecasting in ancient times left many tombs from the Western Zhou, Spring and Autumn, Warring States, Qin, Han, Sui, and Tang dynasties vulnerable to subsequent environmental shifts. During the Little Ice Age after the Song Dynasty, for example, declining groundwater levels and moisture infiltration led to water accumulation inside certain tomb chambers, altering their thermal environment and accelerating the decay of burial objects. Similarly, in the Yuan, Ming, and Qing dynasties—coinciding with the Little Ice Age—tombs originally built in warmer periods were exposed to repeated freeze-thaw cycles in the surrounding soil, increasing the risk of structural damage or collapse. As a result, even early underground tombs in the Guanzhong region remained susceptible to damage under long-term climatic fluctuations. This historical experience highlights a relevant lesson for contemporary practice: in designing and constructing modern underground spaces, it is important to account not only for current climate conditions but also for projected trends in regional climate over a reasonable time horizon. By integrating big data and artificial intelligence into climate forecasting, designers can prioritize present-day functional and environmental needs while also incorporating forward-looking adaptations. Allowing a margin of safety and flexibility in design may thus enhance the resilience of underground structures under future climate scenarios⁵⁷.

During the warm and humid pre-Qin period, most underground tombs in the Guanzhong region were situated on elevated plateaus or higher terrain. The use of higher altitudes helped minimize the accumulation of rainwater and surface water near the tombs, reducing the risk of infiltration into the burial chambers and limiting their exposure to precipitation and surface runoff. In contrast, during the colder and drier Yuan, Ming, and Qing dynasties, underground tombs in the region began to be located more frequently in plain areas. This shift can be attributed to two main factors: first, the reduced concern regarding rainwater intrusion in a drier climate, and second, the influence of increasingly secularized tomb culture, which emphasized closer proximity between burial sites and settlements to facilitate ancestor worship and maintenance by descendants.

A key insight for modern underground space design in the Guanzhong region is to avoid situating functional areas beneath low-lying terrain wherever possible. It is important to ensure that the overlying soil layer does not retain long-term surface water accumulation. Although modern underground structures typically employ reinforced concrete roofs with effective waterproofing systems, any cracking or damage to the roof—combined with water accumulation above—could lead to moisture infiltration. This may compromise the internal environment of the underground space. Therefore, locating important underground functional areas at relatively higher elevations can help minimize the risk of rainwater pooling above the structure, reduce potential water seepage, and contribute to maintaining stable humidity and thermal conditions inside the underground space⁵⁸.

In summary, this study employed archeological data to reconstruct the spatial and geographical characteristics of underground tombs in the Guanzhong region from the Western Zhou through the Qing dynasty. The research identifies evolutionary patterns in the layout and spatial configuration of tombs in this central region, examines underlying factors influencing these patterns, and highlights potential insights from traditional construction practices that may inform modern underground space design. These findings offer a historical and theoretical reference for contemporary underground space design and construction.

While this research provides a systematic analysis of the relationship between climate change and the evolution of tomb structures in the Guanzhong region, several limitations should be acknowledged. First, the reconstruction of historical climate data relies on proxy indicators and regional analogs, which inherently contain uncertainties in temporal resolution and spatial representativeness. Although temperature and precipitation are fundamental climate variables⁵⁹, their coupling effects with other environmental factors—such as wind patterns, soil chemistry, and vegetation cover—were not fully explored, potentially overlooking synergistic impacts on tomb preservation and spatial organization. Second, the archeological dataset, while extensive, remains constrained by uneven preservation and excavation records across dynasties. Tombs from certain periods, particularly those of the Wei, Jin, and Southern and Northern Dynasties, are underrepresented, which may affect the statistical robustness of trend analyses. Furthermore, the study focuses primarily on macro‑scale climatic influences⁶⁰, while non‑climatic factors—such as technological innovations, ritual practices, economic capacity, and political interventions—are discussed but not quantitatively integrated into the analytical model. This limits the ability to fully disentangle climate‑driven adaptations from culturally or socially motivated changes. Finally, while the translation of historical design principles into modern underground space planning offers valuable insights, their direct applicability requires further validation through case‑specific engineering studies and environmental simulations. Future research would benefit from higher‑resolution paleoclimatic reconstructions, expanded archeological sampling, and interdisciplinary approaches that dynamically integrate climatic, cultural, and technological variables⁶¹.